>>44437074This. So many Pokemon could run your team over if you didn't account for them, and packing just one failsafe wasn't enough because z-moves made it easy to remove any potential checks and counters with one good guess.
Gen 7 also barely had any bans from OU. IIRC, Zygarde was the last ban, and the OU council sat on it for many months before finally doing something about it.